ROBOTIC SENSORS
• THE SENSORS ARE THE INPUT OF THE ROBOT
SYSTEM. ALL SENSORY MODULES ARE
INTERFACED TO THE COMPUTING UNIT OF THE
ROBOT.
LIST OF ROBOT SENSORS BASED ON
APPLICATION
• 1. PROXIMITY DISTANCE MEASUREMENT SENSORS
• There are different varieties of distance measurement
sensors are available in the market. There are one
dimensional (1-D), 2D and 3D distance measurement
sensors. Distance measurement sensors are also
known as ‘Range finders’ meaning it can measure the
distance from an observer to a target.
•1.1 One dimensional (1-D) range finders
• In 1-D range finders, the distance
calculation is done line -of -sight, meaning
the distance measurement is through a
straight line from observer to the object.
Examples of the 1D sensors are IR sensors,
Ultrasonic distance sensors, optical timeof-flight (ToF) sensors, etc.
Here are a few models of IR sensors,
ultrasonic distance sensors, and
optical ToF sensors.
• APPLICATIONS:
- SIMPLE OBSTACLE DETECTION AND
AVOIDANCE
1.2 Two dimensional (2-D) range finders
The 2D range finders mainly consist of laser scanners
that can scan a 2D plane and can compute the range
measurements. There are static 2D laser scanner and
a rotational 2D laser scanner.
The static laser 2D scanner can scan only in a limited
range of angles, but rotational scanners can scan up
to 360 degrees. There will not be any movable parts
like motors in static laser scanners, but rotational
scanners will have motors to rotate the laser.
EXAMPLES OF 2D RANGE
FINDERS
Applications:
- Obstacle detection and avoidance
- SLAM, Navigation
- 3D Object detection and segmentation
•1.3 3D range finders
• The 2D laser range finders can find obstacles in a
2D plane, but the 3D range finders can find
obstacles in the real 3D space. Like in 2D range
finders, these range finders can be static or
rotational sensors. Most of the 3D static range
finder sensors can give range measurement in a
specific field of view of the sensor, but there are
some exceptions too. The 3D rotational range
finders can give 360-degree range finding around
the sensor.
EXAMPLES OF 3D RANGE
FINDERS
3D Static range finders & RGB-D Camera
In 3D static range finders, there are no
movable parts. These sensors can be
mounted in one of the robot links. Most of
the RGB-D cameras belong to 3d static
range finder. The RGB-D cameras use IR
projection and reflection technologies to
compute the 3d range. These sensors can
only give the 3D range within a specific
angle.
In this range finders, there are
movable parts. The sensors can
able to scan and compute range
measurements up to 360
degrees. Most of the rotational
3D range finders are LiDARs. The
following sensor gives the 3D
ranges in 360 degrees.
3D Rotational range finders
2. ROBOT ENVIRONMENTAL SENSORS
These sensors are used for
monitoring environmental
parameters like temperature,
humidity, air quality, etc.
•Temperature Sensors: LM 35, TMP36
•Humidity Sensors: DHT22
•Moisture sensor: FC-28
•Wind Speed/ Direction: Anemometer
•Air quality sensors: Grove – Gas
Sensor(MQ2), Grove – Air Quality Sensor
•Radiation measurement sensors: Pocket
Geiger Radiation Sensor
3.MOTION DETECTION SENSORS
Robot motion sensors are for
detecting motion around the robot.
There are several approaches for
detecting motion around the robot
using cameras and LIDARs, but
there are few sensors are
dedicated to this purpose.
Motion detection sensors
Passive Infrared (PIR) Sensors:
This sensor can emit electricity
when an IR radiation hits on the
sensor. Normally humans and
animals can radiate IR radiation, so
this sensor will trigger whenever
an IR radiation hits on the sensor.
Microwave Sensors: This sensor
will send the microwave signals
to the object, and receive the
reflected signals. The analysis
of the disturbance in the
reflected signals can predict the
motion of the object.
Tomographic sensors: This sensor
works on radio waves and it can
detect the motion whenever the
reflected waves get disturbed. This
can cover a large area. These
sensors are a bit expensive,
normally used in the warehouse.
4.POSE ESTIMATION SENSORS
The pose estimation sensors in the
robotic system can compute the
position and orientation of a mobile
robot. The pose of a robot is an
important parameter for
doing autonomous
navigation and localization.
HERE ARE SOME EXAMPLES OF
POSE ESTIMATION SENSORS.
1. Inertial Measurement Unit (IMU):
IMU is a class of devices that reacts
to or senses physical motion
parameters, including acceleration,
rotation, or change in position.
2. Global Position System (GPS):
GPS is a famous satellite-based
radio navigation system. It is
mainly used in outdoor robot
navigation. Most of the high-end
GPS modules come with IMU for
pose estimation.
3. Indoor positioning sensor (Indoor
GPS): GPS is mainly using for
outdoor applications. There are
indoor GPS sensors for indoor
positioning applications too. The
technology of positioning is
different. These sensors are using
beacons and color markers to
navigate in an indoor environment.
5. SPEED MEASUREMENT SENSORS
The speed measurement sensors are
mainly used to determine the wheel
speed of the robot system. If the wheel
speed of the robot is known, we can
compute the distance traveled by the
robot and the position of the robot. The
estimation of robot position from speed
measurement sensors is called
‘Odometry‘.
EXAMPLE OF SPEED MEASUREMENT
SENSORS
Wheel Encoders:
The commonly used speed
measurement sensors in robots are
wheel encoders. The encoder circuit
can trigger whenever a movement in
the robot wheel/motor gear
shaft/motor shaft itself.
Types of Wheel encoders
1. Optical encoders: These encoders
detect the wheel movement using an
optical transmitter like LED and
receiver like photodiode. It uses a
wheel disc in-order to detect these
changes.
2. Magnetic (hall-effect) quadrature
encoders:
These sensors are using a hall-effect
sensor in order to detect the motion
of the wheel. A magnetic disc will be
mounted on the wheel shaft,
whenever the disc moves, this sensor
will trigger.
6. Force/Torque/Touch sensors
- Force/Torque/Touch sensors
give a feel of touch. The robot
can estimate how much
force/torque robot exerting on
the joints or the robot tip(end
effector).
7. Robot audio sensors
• Audio sensors are basically
microphone based circuits that are
either used to detect a sound with
a certain threshold, or processing
the audio signals for speech
recognition, speaker identification,
etc.
Here are some microphone based modules
for detecting sound.
8. Robotic 2D vision sensors
• These sensors are mainly digital
cameras. There are different
types of digital cameras available
in the market. In robots, you can
use from ordinary webcam up to
industrial cameras like point grey.
Here are a few examples of 2D
cameras.